Peptide COA Guide: How to Read & Verify a Certificate of Analysis
Published: 2026-03-07Updated: 2026-03-10Category: Guides
A Certificate of Analysis (COA) is the most important quality document for research peptides. But not all COAs are equal — some vendors fabricate them, photoshop results, or use internal testing with no independent verification. This guide teaches you what to look for.
What a Legitimate COA Contains
| Element | What It Tells You | Red Flag If Missing |
|---|
| Batch/Lot Number | Links the COA to your specific vial | Generic COA that applies to "all" batches |
| HPLC Purity % | Percentage of target compound vs impurities | No percentage or vague "high purity" claim |
| HPLC Chromatogram | Visual trace showing the separation of compounds | Purity % with no supporting chromatogram |
| Mass Spectrometry (MS) Data | Confirms molecular identity (molecular weight) | Purity claim with no identity confirmation |
| Observed vs Theoretical MW | Should match within 0.1% of expected molecular weight | No molecular weight data at all |
| Testing Laboratory Name | Independent third-party verification | No lab named, or "internal testing" |
| Date of Analysis | Confirms recency of testing | No date or very old date |
HPLC Chromatogram: What to Look For
A chromatogram shows peaks corresponding to each compound in the sample. The target peptide should appear as a single, sharp dominant peak with minimal secondary peaks. The purity percentage is calculated as the target peak area divided by total peak area. Research-grade peptides should show ≥98% purity, with premium suppliers achieving ≥99%.
Red flag: If a chromatogram shows multiple large peaks of similar height, the sample contains significant impurities. If no chromatogram is provided at all, the purity percentage cannot be independently verified.
Mass Spectrometry: Identity Confirmation
HPLC tells you how pure the sample is; MS tells you what it is. The observed molecular weight should match the theoretical molecular weight of the target peptide within standard instrument tolerance. For example, BPC-157 has a theoretical MW of 1419.53 Da — the observed MW on the COA should be within ~1.4 Da of this value.
Third-Party vs Internal Testing
Internal testing means the vendor tested the product themselves. They have a financial incentive to report favorable results. Third-party testing by an independent laboratory eliminates this conflict of interest. At Pepta Labs, every batch is tested by an independent lab — COAs are downloadable from every product page before you purchase.
Batch Number Verification
The batch number on your COA should match the batch number on your vial label. If they don't match, the COA doesn't apply to your specific product. This is a basic but frequently overlooked verification step. Some vendors use one COA across all batches — this is not batch-specific testing.
All information is sourced from published peer-reviewed literature and provided for educational purposes only. This content does not represent claims about products sold by Pepta Labs. All products are chemical reference materials for in-vitro laboratory research only. Not for human or animal consumption. See
Terms of Service and
Compliance Policy.
Browse Research Compounds
34+ peptides. Third-party COAs. Free US shipping.
View Catalog →